Apparatus and method for simulating bronchial resistance or dilation

ABSTRACT

An apparatus and method for simulating bronchial resistance or dilation in real time in an integrated patient simulator during simulated medical procedures is realized by a manikin having a simulated trachea and a simulated lung, a conduit interconnecting the simulated trachea and the simulated lung for propagating a flow of gas, and a restricting device for variably restricting the flow of gas through the conduit. The restricting device includes a nautilus shaped cam and a stepper motor for rotating the cam such that a selected surface of the cam is disposed within a opening in the conduit so as to continuously vary the size of the opening.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of Applicant's U.S. Ser. No.08/188,383, filed Jan. 27,1994, now U.S. Pat. No. 5,584,701, which, inturn, is a continuation-in-part of Applicant's U.S. Ser. No. 07/882,467,filed May 13, 1992, issued as U.S. Pat. No. 5,391,081, the contents ofall of which are hereby incorporated by this reference.

BACKGROUND

1. Field of the Invention

This invention relates to an integrated patient simulator and methods ofusing the same. In particular, this invention discloses an improvedpatient simulator capable of realistically simulating nerve stimulation,lung movement, lung volume measurement and lung breathing noise,administration, detection, identification and quantification ofmedicaments and fluids introduced during simulated surgery. bronchialresistance, computer controllable compliances and also possessing animproved computational configuration, an electric cardiacsynchronization pulse, audible heart and lung sounds, simulation ofcontinuous blood gases, pulmonary artery (PA) catheter inflationdetection, difficult airway, spontaneous breathing and otheranesthesiological indications, and gas exchange via a mass-flowcontroller.

2. Background of the Invention

Currently, a new resident in medicine will receive a very limitedduration of didactic teaching about the principles of particular medicalprocedures, such as anesthesia, before delivering care to his/her firstreal patient. The resident is then faced with a now and unfamiliarenvironment while shouldering the tremendous responsibility of caringfor an ill and sometimes anesthetized patient. Similarly, experiencedphysicians who require continuing medical education, refresher courses(e.g. handling of rare ailments and situations) or familiarization withnewly introduced and/or technologically sophisticated equipment orprocedures do not have the opportunity for hands-on practice in arealistic environment, without risk to a patient. Of course, theseundesirable situations also apply to other disciplines such as alliedhealth care and veterinary medicine, for instance.

The patient simulator disclosed in U.S. patent application Ser. No.07/882,467, now U.S. Pat. No. 5,391,081, addresses the above-mentioneddeficiencies in medical, allied health care and veterinary education.The improved self-regulating full-scale patient simulator technologydescribed herein comprises further embodiments of a patient simulator.

The lung portion of the integrated patient simulator disclosed hereinconsumes and/or produces gases including oxygen, carbon dioxide,nitrogen, nitrous oxide and volatile anesthetics. Under the control of amathematical model of human physiology implemented on a computer, uptakeand delivery of the above mentioned gases is computed by the uptake anddelivery module of the physiological model. The computed uptake anddelivery is then physically created by gas substitution in the hardwaremodule for simulating gas exchange in the lung simulator portion of thepatient simulator. The lung will also simulate spontaneous inspirationwith computer control of tidal volume (VT), respiratory rate (RR) andfunctional residual capacity (FRC) and will also allow the simulation ofa cough. In addition, the lung will exhibit the desired lung mechanicsand gas exchange when mechanically or manually ventilated.

The patient simulator system of this invention has several componentsincluding lung mechanics (software and hardware); gas exchange (softwareand hardware); a physiologic model (software); cardiovascular; uptakeand distribution; neuromuscular system;pharmacokinetics/pharmacodynamics; physiologic control models; and aunique linking of the different subsystems of the patient simulator sothat the patient responds realistically to inputs from thetrainee/student.

A major improvement of the lung/patient simulator is that it allowsrealistic action/reaction interplay between the actions of the trainee,responses of the simulated patient, data shown on the monitors andsubsequent actions by the trainee. Another significant improvement thatdistinguishes the lung/patient simulator from similar systems is thatits software and hardware are self-regulating. The present hybrid(mechanical and mathematical) lung model regulates itself regardless oftype of gas (air, anesthetics, hypoxic, etc.) inhaled, and,surprisingly, even the blunting of physiological control mechanisms(e.g. ventilatory response to carbon dioxide) is self-regulated.

The present patient simulator is an integrated, self-regulating system.For instance, in a non-self-regulating system, an awkward inputsituation would invariably lead to physiologically implausible behaviorfrom the system or such stimuli would result in an inability of thesystem to handle the input at all. A self-regulating system is morerobust in the accommodation and simulation of unplanned events becauseit will still provide an appropriate response. Thus, self-regulation ishighly desirable, yet glaringly absent from the prior art.

For instance, if the trainee accidently ventilates the lung with ahypoxic (lacking oxygen) gas mixture (e.g. pure argon gas), aconventional system may not be able to react appropriately. However, thepresent invention provides an integration of relevant systems such that,through self-regulation, appropriate simulated manifestations of hypoxiawould be produced in the various output devices of the patientsimulator, e.g. increased breathing rate and heart rate.

As another example, those skilled in the art are aware that increasedCO₂ levels in the lung will cause hyperventilation. Hyperventilationresults in lowering of CO₂ levels in the lungs due to washing away ofthe carbon dioxide. In a nonself-regulating patient simulator, increasedlung CO₂ may or may not lead to increased ventilation. If no increaseoccurs, the reality of the simulation is decreased, thereby lesseningthe teaching value of the simulation.

Thus, it is clear that self-regulating systems hold clear advantagesabove non-self-regulating systems.

Furthermore, a means for adequately handling the injection of liquidanesthetic into the breathing circuit has been attempted by otherresearchers. The problems encountered in the prior art included (a)freezing of the location where the liquid anesthetic is introducedbecause of the heat of vaporization extracted from the surrounding asthe liquid anesthetic evaporates, (b) pooling of the injected liquidthrough lack of heat to vaporize the liquid anesthetic and (c)uncontrolled evaporation of the anesthetic liquid from the syringe tothe breathing circuit (i.e, the tubing or conduit assembly whichphysically connects the anesthesia machine or ventilator to thepatient/manikin). The instant integrated patient simulator solves theseproblems by providing a means as usable not only in the simulation butin real life anesthesia applications.

A real life practitioner must be able to react to a patient who isundergoing a degree of bronchial restriction. Therefore, it is highlydesirable for a patient simulator to be able to simulate bronchialresistance where the restriction of gas flow may be varied upon acontinuum. Without manual intervention, such capability is lacking inthe prior art systems.

In a full-scale patient simulator, it is necessary to be able tosimulate changes in bronchial resistance. In a full-scale simulatorusing real gas flows, independent computer-controlled variable orifices(with maximum openings of 0.5" diameter) placed in the bronchi wouldallow simulation of changes in bronchial or airway resistance. No priorart devices (e.g., photographic camera iris diaphragms) were found whichcould simulate variable bronchial resistances in the relevant diameterrange. Furthermore, a device capable of allowing a suction catheter topass down the bronchus was preferable. Thus, the present invention couldnot use butterfly valves with an internal diameter of 0.5".

Another possible embodiment was a stepper motor actuated cam or leverthat presses a flexible conduit closed. However, because the steppermotor would have needed to be overly large in order to provide the forcenecessary to maintain the flow area completely closed and capable ofholding a pressure of 120 cm H₂ O, one of the design specifications, itwas highly desirable and necessary to design an alternativecomputer-controlled variable orifice device.

During simulation, it is preferable if the drugs and IV fluidadministered by the trainee to the simulated patient are automaticallysensed and input into the computer, rather than having to depend on thesimulation instructor to recognize and manually enter the drug or IVfluid type, concentration and dose administered to the patient. Thus, inprior systems, the simulation instructor might be distracted and missthe administration of the drug or IV fluid by the student or mightmanually enter into the simulation controller the wrong type,concentration or dose of the drug or IV fluid.

In addition, the amount of drug and/or IV fluid administered by thestudent is a critical input to the physiological model of the patientbecause the response of the patient is dose and volume-dependent. Theamount of IV fluid dripped into the patient is also a parameter thatneeds to be quantified if the fluid balance of the simulated patient isto be correctly modelled. It does not appear that prior art systems havecontemplated a means for quantification of drug administered. As In drugidentification, a system that will allow quantification of the amount ofdrug or IV fluid injected via an intravenous (IV) line without the needfor a human observer is highly desirable.

U.S. patent application Ser. No. 07/882,467 disclosed and claimed oneembodiment of distributed processing network for Implementing thecomputer portions of the current patient simulator: a ring-shaped arrayof single-board computers (i.e., DACS PAN--Data Acquisition and ControlSystem).

It has been found that a star configuration for a network of singleboard computers is more preferable. The extent of computational powerand parallel processing required for simulating a patient's differentphysiological subsystems is facilitated by a distributed processingnetwork. For example, one computer takes modulates the mechanical lungwhile another controls the palpable pulses. The ring network is lessrobust than a star network configuration because if one of the singleboard computers becomes non-functional, the entire network ceases tooperate. In the star network configuration, the network will stillfunction even if one of the computers on the network fails.

The realism of a simulation would be marred if the different signs orvariables dependent on the cardiac rhythm were at different frequencies(e.g., an ECG heart rate of 70 beats per minute (bpm) but a pulse ratefrom the pulse oximeter of 90 bpm). A mechanism that allowssynchronization of all cardiac related events is, therefore, highlydesirable and necessary for a realistic patient simulator.

The realism of a patient simulator would also be compromised if thesimulator lacked audible heart, lung and breathing sounds emanating fromthe appropriate portions of the simulator. In addition, spontaneousbreathing is highly desirable and adds to the realism of the patientsimulator.

In addition, a realistic patient simulator should be able to simulatethe monitoring of continuous blood gases. Simulation of continuous bloodgases monitoring is highly desirable in light of recent technologicaladvances implementing such technology in the everyday practice ofspecialists. Furthermore, it is highly desirable that a patientsimulator have a means for detecting pulmonary artery (PA) catheterinflation.

Also, it is desirable to have a patient simulator capable of simulatinga difficult airway. Difficult airway may be caused by a number offactors, such as an allergic reaction. In a difficult airway situation,the patient's trachea closes and prevents the flow of air in and out ofthe patient's lungs. Thus blocked, it is not possible to insert throughthe trachea an endotracheal tube (ETT) for securing the airway. It ishighly desirable to provide a patient simulator capable of simulatingthis potential complication so that a trainee may be taught the properresponse techniques such as a cricothyrotomy.

In addition, a difficult airway is a potentially lethal incident whichanesthesiologists and other practitioners will likely encounter inactual patients. The American Society of Anesthesiologists has declaredthat is essential for any anesthesiologist to know how to handle such asituation as one of his or her practice parameters. Thus, the patientsimulator provides a risk-free way to asses whether a trainee hassuccessfully learned how to handle a difficult airway.

It is also desirable to provide a patient simulator capable of efficientand realistic gas exchange. Although a previous embodiment of thepatient simulator contained a gas exchange module, the current modulediffers in important ways. Most importantly, the patient simulatordisclosed herein uses mass flow controllers instead of frequencymodulated valves as in the previous embodiment. Modulated valvesprovided inaccurate control over the flow rate of the different gases.In addition, maximum flow rate was limited in the prior embodiment in anunrealistic fashion which resulted in a unrealistically small differencebetween inhaled and exhaled oxygen levels. Finally, the frequencymodulated valves resulted in inconsistent signals transmitted to thecapnogram (depiction of CO₂ level over time) which manifested themselvesas ripples instead of straight lines, especially during plateau portionsof the exhalation.

In addition, instead of a "copper kettle" Venitrol vaporizer being usedto introduce vaporized volatile anesthetic into the lung bellows, asyringe pump with a novel copper device is used in the presentinvention. In copper kettle systems, a carrier gas (generally O₂) isbubbled through a pool of liquid anesthetic contained in a solid coppervaporizer. The use of the syringe pump eliminates the necessity of usinga carrier gas per se thus simplifying the behavior of the gas exchangesubsystem in general.

Realistic simulation of gas exchange is necessary because it allows theuse of real or modified medical gas analyzers such as those used in realoperating rooms. Other simulators do not model gas exchange at all.Instead, other simulators in the art bleed CO₂ at variable rates intothe bellows representing the simulated lungs. Thus, the simulators areincapable of simulating even the most rudimentary gases being exchangedsuch as oxygen. Nor are those systems capable of simulating theconsumption or excretion of the amount of volatile anesthetics.

In addition, when an oxygen analyzer is used to sample the flow of gasesinto and out of a real patient's lung, exhaled oxygen will be notablylower than inhaled oxygen due to consumption in the patient's lungs.Unlike other simulators, the patient simulator of this invention iscapable of realistically portraying to external monitoring equipment thedifferential between inspired and expired oxygen concentration. Whenother simulators are linked to an oxygen analyzer, the insiparatory andexpiratory oxygen levels will be identical either indicating gravehealth problems to the patient or a serious breakdown in the realism ofthe simulation. Thus, the accurate modeling of gas exchange, asaccomplished by the instant invention is highly desirable.

SUMMARY OF THE INVENTION

The present invention discloses a self-regulated lung in a manikin foruse in real time in an integrated patient simulator during simulatedmedical procedures, comprising at least one bellows capable of receivingand expelling a gas, a means for actuating the bellows between expandedand contracted states depending upon a time- and event-based script, acomputer model or a combination of a time- and event-based script and acomputer model based on the physiological state of the patientsimulator, at least one mass flow controller capable of directing thegas into the bellows when the bellows expands in volume, a first conduitinterconnecting the mass flow controller and the bellows, a vane pumpcapable of expelling the gas from the bellows when the bellows contractsin volume, and a second conduit interconnecting the bellows and the vanepump. In a preferred embodiment, the means for actuating the bellowsbetween an expanded and a contacted state comprises a double actingpiston attached to the bellows and a first constant pressure and asecond variable pressure acting on respective sides of the double actingpiston whereby varying the second variable pressure causes the bellowsto expand or contract.

In another embodiment, the present invention provides a self-regulatedlung in a manikin further comprising a pressure sensor situated insidethe bellows, a syringe pump disposed along the fit conduit intermediatethe bellows and the mass flow controller, wherein the syringe pump iscapable of injecting a volatile drug into the bellows, and a gasanalyzer disposed along the second conduit intermediate the bellows andthe vane pump, wherein the gas analyzer is capable of assaying theexpelled gases.

In addition, another embodiment provides an apparatus for continuouslyinjecting and volatilizing a volatile drug in real time in an integratedpatient simulator during simulated medical procedures, comprising amanikin, a supply of gas, at least one output device associated with themanikin, a means for volatilizing a drug administered to the manikincomprised of a thermal conductor defining a gas propagating cavitydisposed therethrough and a sintered insert disposed within the gaspropagating cavity, the thermal conductor further defining a needleaccepting cavity which communicates the exterior of the thermalconductor with the interior of the insert, wherein the needle acceptingcavity is capable of accepting a hypodermic needle such that the tip ofthe hypodermic needle is in contact with the sintered insert when theneedle is fully inserted into the volatilizing means, and wherein thegas propagating cavity is capable of permitting the flow of the gastherethrough such that the drug upon evaporation in the sintered insertis carried through the gas propagating cavity by the supply of gasflowing continuously therethrough, a conduit interconnecting the supplyof gas with the gas propagating cavity, and programmed computing meansassociated with the receiving means for calculating a simulated responseto the drug and for actuating the output device to simulate the effectsof the drug according to a time- and event-based script, a computermodel or a combination of a time- and event-based script and a computermodel based on the physiological state of the patient simulator. In apreferred embodiment the sintered insert is comprised of brass and thethermal conductor comprises a cylinder of copper.

Another embodiment describes an apparatus for simulating bronchialresistance or dilation in real time in an integrated patient simulatorduring simulated medical procedures, comprising a manikin with asimulated trachea and a simulated lung, a conduit interconnecting thesimulated trachea and the simulated lung for propagating the volume ofgas, a volume of gas flowing within the conduit, and a means in theconduit for restricting the flow of the volume of gas therethroughwhereby a bronchial opening is simulated. In a preferred embodiment,this conduit is interrupted by an opening and the restricting meanscomprises rotating means and a nautilus shaped cam mounted on therotating means so as to present a selected surface thereof within theopening so as to continuously vary the size of the opening.

In addition, the present invention provides an apparatus for detectingand identifying a drug or fluid administered in real time in anintegrated patient simulator during simulated medical surgery,comprising a manikin, a bar code affixed to an implement for admiring afluid to the manikin, wherein the implement is selected from the groupconsisting of an intravenous drip bag and a syringe and wherein the barcode indicates the type and volume of fluid contained within theimplement, and a bar code scanning means for detecting and identifyingthe fluid administered by the bar code affixed to the implement. In arelated embodiment, there is provided an apparatus for quantifying theamount of a fluid administered in real time In an integrated patientsimulator during simulated medical surgery, comprising a manikin, areservoir associated with the manikin for containing a fluidadministered to the manikin, a means for delivering the fluid to thereservoir, weighing means for calculating an initial weight of thereservoir and a second weight of the reservoir upon a preselected event,means for calculating the difference between the second weight of thereservoir and the initial weight of the reservoir, and programmedcomputing means for calculating a simulated response to the quantity offluid delivered to the reservoir according to a time- and event-basedscript, a computer model or a combination of a time- and event-basedscript and a computer model based on the physiological state of thepatient simulator.

In a further embodiment, there is provided an apparatus forsynchronizing output devices related to a cardiac rhythm in real time inan integrated patient simulator during simulated medical surgery,comprising a manikin, at least one output device associated with themanikin, a first programmed computing means capable of generating atleast one electric cardiac rhythm synchronizing pulse, a distributedprocessing network associated with the manikin, and a second programmedcomputing means associated with the manikin for calculating a simulatedresponse to the cardiac rhythm synchronizing pulse and for actuating viathe distributed processing network the output device associated with themanikin in real time according to a time- and event-based script, acomputer model or a combination of a time- and event-based script and acomputer model based on the physiological state of the patientsimulator. In a preferred embodiment, the distributed processing networkis a star network. In a further preferred embodiment, the output devicemay be a radial pulse emulating means.

The present invention also provides an apparatus for simulating soundsof breathing in real time in an integrated patient simulator duringsimulated medical procedures, comprising a manikin, a means associatedwith the manikin for continuously determining the volume of at least onelung bellows associated with the manikin, means for calculating a firstderivative of the bellows volume over time to determine the phase of therespiratory cycle and for calculating a second derivative of the bellowsvolume over time to determine a transition in phase of the respiratorycycle, and sound output means for outputting, based upon the first andsecond derivatives of the bellows volume over time, an audible sound ofbreathing corresponding to an appropriate physiological sound. In apreferred embodiment, the sound simulating apparatus has a means fordetermining whether an abnormal condition is effecting the physiologicalstate of the patient simulator and means for altering the audible soundof breathing corresponding to the appropriate physiological sound basedupon the abnormal physiological condition effecting the physiologicalstate.

A similar embodiment encompasses an apparatus for simulating heartsounds in real time in an integrated patient simulator during simulatedmedical procedures, comprising a manikin, a means for continuouslydetermining the physiological state of the patient simulator, and soundoutput means for outputting, based upon the physiological state, anaudible heart sound corresponding to an appropriate physiological sound.In a preferred embodiment, the heart sounds apparatus further comprisesa means for determining whether an abnormal condition is effecting thephysiological state of the patient simulator and means for altering theaudible heart sound corresponding to the appropriate physiological soundbased upon the abnormal condition effecting the physiological state.

Another similar embodiment encompasses an apparatus for simulating lungsounds in real time in an integrated patient simulator during simulatedmedical procedures, comprising a manikin, a means for continuouslydetermining the physiological state of the patient simulator, and soundoutput means for outputting, based upon the physiological state, anaudible lung sound corresponding to an appropriate physiological sound.Preferably the lung sounds apparatus further comprises a means fordetermining whether an abnormal condition is effecting the physiologicalstate of the patient simulator and means for altering the audible lungsound corresponding to the appropriate physiological sound based uponthe abnormal condition effecting the physiological state.

The integrated patient simulator of the instant invention also providesan apparatus, for simulating the determination of continuous blood gasesin real time in an integrated patient simulator during simulated medicalprocedures, comprising a manikin, a mock continuous blood gas machineassociated with the manikin and having a means for simulating an output,means for determining the physiological state of the patient simulator,and a means for delivering a signal to the mock continuous blood gasmachine according to the physiological state whereby an output issimulated on the means for simulating an output.

In addition, another embodiment of the integrated patient simulator isan apparatus for simulating a difficult airway in real time in anintegrated patient simulator during simulated medical procedures,comprising a manikin having a neck, an airway within the neck which isflexible or crushable along a portion of its length, a programmablecomputing means for calculating a simulated response to thephysiological state of the patient simulator in real time according to atime- and event-based script, a computer model or a combination of atime- and event-based script and a computer model, and based on thecalculated simulated responses a means for constricting, sealing orcrushing the portion in the airway. In a preferred embodiment, theflexible airway comprises a conduit having a flat back wall havingopposed, parallel sides therealong and an exterior surface and anopposed interior surface, a semicircular front wall having edgesconnected to the respective sides of the flat back wall and having aninterior surface and an opposed exterior surface, a plunger disposedadjacent the exterior surface of the flat back wall, a means foractuating the plunger whereby the plunger engages the exterior surfaceof the flat back wall so as to move the interior surface of the flatback wall a selected distance toward the interior surface of thesemicircular wall. In a more preferable embodiment, the plunger iscomplimentarily shaped to the interior surface of the semicircular wall.

In addition to the above apparatuses, there are also provided a varietyof method embodiments. First, there is a method of simulating aself-regulated lung in real time in an integrated patient simulatorduring simulated medical procedures using a manikin, comprising thesteps of expanding in volume at least one bellows by a bellows actuatingmeans, directing to the bellows a gas flow delivered by at least onemass flow controller, continuously monitoring the pressure inside thebellows, contracting in volume the bellows by the bellows actuatingmeans continually expelling the gas through a vane pump, and analyzingthe expelled gas flow prior to its entry into the vane pump. In apreferred embodiment, the method further comprises the step ofcontinuously injecting via a syringe pump a preselected amount of avolatile drug into the gas flow intermediate the mass flow controllerand the bellows. In addition, a preferred embodiment uses a bellowsactuating means comprised of a first constant pressure and a secondvariable pressure acting on respective sides of a double acting pistonwhereby varying the second variable pressure causes the bellows tosimulate, expand or contract depending upon a time- and event-basedscript, a computer model or a combination of a time- and event-basedscript and a computer model based on the physiological state of thepatient simulator.

In another embodiment, the present invention provides a method ofsimulating a physiological response to a drug in real time in anintegrated patient simulator during simulated medical procedures using amanikin, comprising the steps of directing a volatile drug to a manikinwhich has a drug volatilizing means, wherein the drug volatilizing meanscomprises a thermal conductor defining a gas propagating cavity disposedtherethrough and a sintered insert disposed within the gas propagatingcavity, the thermal conductor further defining a needle accepting cavitywhich communicates the exterior of the thermal conductor with theinterior of the insert, wherein the needle accepting cavity is capableof accepting a hypodermic needle such that the tip of the hypodermicneedle is in contact with the sintered insert when the needle is fullyinserted into the receiving means, flowing a gas through the gaspropagating cavity such that the drug upon evaporation on the sinteredinsert is carried through the gas propagating cavity by the gas to adrug analyzing means, detecting by the drug analyzing means the kind ofdrug administered, using that information in computing a simulatedresponse on at least one output device associated with the manikin so asto provide a simulated response in accordance with an appropriatephysiological response to the drug.

In yet another embodiment, the present invention provides a method ofsimulating bronchial resistance or dilation in real time in anintegrated patient simulator during simulated medical procedures using amanikin, comprising the step of actuating a means associated with themanikin for restricting a simulated bronchial opening by rotatablyengaging a cam that presents a selected surface thereof within anopening in a conduit so as to vary the size of the opening.

A further embodiment provides a method of simulating non-linearcompliances in real time in an integrated patient simulator duringsimulated medical procedures using a manikin, comprising the steps ofcomputing the volume of at least one bellows and supplying a firstconstant pressure and a second variable pressure acting on respectivesides of a double acting piston capable of actuating the bellows wherebyvarying the second variable pressure causes the bellows to exhibit thedesired compliance force on the bellows according to a time- andevent-based script, a computer model or a combination of a time- andevent-based script and a computer model based on the physiological stateof the patient simulator.

Another embodiment of the present invention provides a method ofdetecting and identifying a drug or fluid administered in real time inan integrated patient simulator during simulated medical surgery using amanikin, comprising the steps of scanning a bar code affixed to animplement selected from the group consisting of an intravenous drip bagand a syringe, wherein the bar code indicates the type and concentrationof fluid contained within the implement detecting and identifying thedrug administered by the scanned bar code.

Furthermore, there is provided an embodiment of a method of quantifyingthe amount of a fluid or drug administered in real time in an integratedpatient simulator during simulated medical surgery using a manikin,comprising the steps of calculating an initial weight of a reservoir forcontaining a fluid administering the fluid to the reservoir, detecting asecond weight of the reservoir at a preselected event after theadministration of the fluid, computing the difference between the secondweight of the reservoir and the initial weight of the reservoir, andbased on the difference, determining a simulated response to the fluidaccording to a time- and event-based script, a computer model or acombination of a time- and eventbased script and a computer model basedon the physiological state of the patient simulator.

In addition, the present invention provides a method of synchronizingcardiac rhythm related events in real time in an integrated simulatorduring simulated medical procedures using a manikin, comprising thesteps of transmitting throughout a distributed processing networkassociated with the integrated patient simulator at least one electricpulse corresponding to a cardiac rhythm synchronizing pulse andcalculating a physical response to the cardiac rhythm synchronizingpulse in at least one output device associated with the manikin. In apreferable embodiment, the distributed processing network is a starnetwork. In an even more preferable embodiment, there is a further stepof actuating the at least one output device such as a radial pulseemulating means.

In addition, the present invention provides a method of simulatingsounds of breathing in real time in an integrated patient simulatorduring simulated medical procedures using a manikin, comprising thesteps of continuously determining the volume of at least one bellow,associated with the manikin, calculating a first derivative of thebellows volume over time to determine the phase of the respiratorycycle, calculating a second derivative of the bellows volume over timeto determine a transition in phase of the respiratory cycle, anddirecting, based upon the first and second derivatives of the bellowsvolume over time, thorough a sound outputting means an audible sound ofbreathing corresponding to an appropriate physiological sound. In apreferred embodiment, the method further comprises the steps ofdetermining whether an abnormal condition is effecting the physiologicalstate of the patient simulator and altering the audible sound ofbreathing corresponding to the appropriate physiological sound basedupon the abnormal condition effecting the physiological state.

Similarly, another embodiment provides a method of simulating heartsounds in real time in an integrated patient simulator during simulatedmedical procedures using a manikin, comprising the steps of continuouslydetermining the physiological state of the patient simulator anddirecting, based upon the physiological state, through a soundoutputting means an audible heart sound corresponding to an appropriatephysiological sound. Preferably, this method further comprises the stepsof determining whether an abnormal condition is effecting thephysiological state and altering the audible heart sound correspondingto the appropriate physiological sound based upon the abnormal conditioneffecting the physiological state.

In a related embodiment, there is a method of simulating lung sounds inreal time in an integrated patient simulator during simulated medicalprocedures using a manikin, comprising the steps of continuouslydetermining the physiological state of the patient simulator anddirecting, based upon the physiological state, through a soundoutputting means an audible lung sound corresponding to an appropriatephysiological sound. In a preferable form, this method further comprisesthe steps of determining whether an abnormal condition is effecting thephysiological state and altering the audible lung sound corresponding tothe appropriate physiological sound based upon the abnormal conditioneffecting the physiological state.

Another embodiment discloses a method of simulating the monitoring ofcontinuous blood gases in real time in an integrated patient simulatorduring simulated medical procedures using a manikin, comprising thesteps of continuously determining the physiological state of the patientsimulator, computing appropriate blood gas information based on thephysiological state, and delivering a signal to a mock continuous bloodgas machine according to the physiological state whereby an output issimulated.

In addition, there is a provided an embodiment which is a method ofsimulating a difficult airway in real time in an integrated patientsimulator during simulated medical procedures using a manikin,comprising the steps of calculating a simulated response to thephysiological state of the patient simulator according to a time- andevent-based script, a computer model or a combination of a time- andevent-based script and a computer model, and based on the appropriatesimulated response, constricting a flexible airway in the neck of themanikin.

BRIEF DESCRIPTION OF THE FIGURES OF DRAWINGS

FIG. 1 is a perspective full view of the present integrated patientsimulator with the subsystems included therein indicated;

FIG. 2 is a schematic view of the lung of the integrated patientsimulator of the present invention;

FIG. 3 is a cut-away perspective view of a means for accepting andvaporizing a liquid anesthetic;

FIG. 4 is a cut-away perspective view of a computer-controlled,motorized variable flow orifice for insertion in the bronchus with aportion of the orifice cutaway for clarity;

FIG. 5 is schematic view of a system for detection, identification andquantification of drug and fluid administered to the patient simulator;

FIG. 6 is a schematic of the ring configuration distributed processingnetwork of the present invention;

FIG. 7 is a schematic of a star configuration distributed processingnetwork and a schematic of the path for an electric cardiacsynchronization pulse throughout the star configuration distributedprocessing network;

FIG. 8 is a perspective view of the means for simulating a difficultairway;

FIG. 9 is a schematic showing the placement of speakers for emittingheart and lung sounds;

FIG. 10 is a cut-away perspective view of an apparatus for detecting theinflation of a pulmonary artery catheter balloon where the balloon isun-inflated; and

FIG. 11 is a cut-away perspective view of an apparatus for detecting theinflation of a pulmonary artery catheter balloon where the balloon isinflated.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS OF THE INVENTION

One embodiment of the current invention comprises a computer-basedphysiologic model covering the following subsystems: cardiovascular;uptake and distribution; neuromuscular;pharmacokinetics/pharmacodynamics and physiologic control models. Alsoincluded is a unique way of linking the different subsystems torealistically simulate the interactions between the subsystems and thecontrol system in response to the actions of a trainee, student, orother user (including input from both a computer peripheral such U amouse/keyboard, wired remote keypad, wireless remote control unit,barcode reader and from sensors physically embedded in the full scalelung/patient simulator).

A significant part of a patient simulator useful for traininganesthesiologists and other physicians comprises a subsystem to performgas exchange. The lung model on the instant integrated patient simulatorconsumes and produces gases, just like a human lung. Uptake andexcretion of O₂, CO₂, N₂, N₂ O and volatile anesthetic gases arephysically created and simulated, based on the measured concentrationsin the bellows of the simulated lung and in a software modelrepresenting uptake, distribution, storage, consumption, and/orproduction in the body. Lung perfusion is also accounted for in thismodel by modeling of the cardiovascular subsystem of the patient beingsimulated by the physiological model. Alveolar ventilation is dependenton the lung mechanics and, in the, case of spontaneous breathing, isdriven by the physiologic control and pharmacokinetics/pharmacodynamicsmodels. See Guyton, A. C., Textbook of Medical Physiology (8th ed.), W.B. Saunders Co., Philadelphia, 1991.

The lung model portion of the patient simulator is capable of simulatingspontaneous breathing with computer control of tidal volume (VT) andrespiratory rate (RR). Spontaneous movement of the bellows is driven byan analog muscle pressure signal to simulate inspiration, activeexpiration, coughing, and different spontaneous breathing patterns (I/Einhalation/exhalation! ratio, respiratory rate, respiratory patternsassociated with light anesthesia. The respiratory rate is the frequencyof the muscle pressure signal while tidal volume depends on theamplitude of the muscle pressure signal as well as other airwayparameters such as bronchial resistances and lung-thorax compliances).The muscle pressure signal is generated by the physiologic control modelbased on arterial blood and O₂ and CO₂ content. The signal is convertedby a digital to analog converter into a physical signal directed to theelectronic pressure regulators (EPRs). The real and timevariable voltagethus obtained is fed to the subsystems of the patient simulatorincluding the electronic pure regulator (EPR). The O₂ and CO₂ contentsarm variables of an uptake and distribution model, with the gasconcentrations in the bellows as an additional input. Under normaloperating conditions (i.e., non-occluded airway and normal gascirculation), normal arterial O₂ and CO₂ contents are-maintained.Depression of spontaneous breathing by the influence of anesthetic drugson the respiratory center and/or by the effect of muscle relaxantsdirectly on the respiratory muscles is provided by thepharmacokinetic/pharmacodynamic software models. In addition, normal andabnormal breath sounds are synchronized with the bellows movement.

Furthermore, variable resistances under software control can be variedduring the respiratory cycle to simulate partial collapse of the airwaysduring expiration. This variability includes non-linear computercontrolled compliances (i.e., the inverse of the stiffness of the lung)and computer controlled functional residual capacity (FRC). Existingsimulators with lung modeled are capable of linear compliance only. Thisis unrealistic in that the human lung exhibits a compliance (volumeversus pressure) curve which is sigmoidal in nature.

Non-linear compliances allow the simulation of variable stiffness of thelung. This is accomplished via double acting pneumatic pistons asdescribed herein. Then, passive forces resulting from the non-linearlung- thorax- diaphragm compliances are computed, taking into accountlung volume and intrapleural volume. An intrathoracic pressure isgenerated, affecting circulation and, thereby, gas exchange. Theresulting forces on the lung bellows are realize through a double actingpiston disclosed more fully herein. Compliances and target or modeledintrapleural volumes are under software control.

Thus, with the above-described stimuli, the patient simulator is able togenerate various clinical signs including a sound storage and triggeringmechanism and localization of sound sources/speakers. In particular,speakers have been localized to simulate both heart and lung sounds inlocations generally known to those skilled in the art. See. generally.FIG. 1. Finally, the patient simulator can generate an electrocardiogram(ECG) spike synchronization pulse which is distributed over the networkfor use by all cardiovascular related signals, variables or parameters.

Furthermore, the simulation of blood gas values to corroborate/supportscenarios being played has been implemented. Also disclosed is thesimulation of of detection of pulmonary artery (PA) catheter ballooninflation and associated changes in the PA pressure.

The gas substitution technique together with the physiological softwaremodels create a self-regulating lung that changes Its own breathingpattern. Specifically, the patient simulator can change its inspiratorymuscle pressure waveform to maintain a preset level of arterial/alveolarpCO₂ and pO₂ (partial pressures). The double acting piston mechanism(including a shaft encoder) and its self-regulating software modelcreate spontaneous breaths of variable size and shape along withindependently variable compliance and independently variable bronchialresistance. Thus, the patient simulator disclosed herein contains ahybrid (mechanical and mathematical) lung model which regulates itselfregardless of what type of gas (air, anesthetics, hypoxic, etc.) isinhaled. In addition, even the blunting of physiological controlmechanisms (e.g., ventilatory response to carbon dioxide) isself-regulated.

Therefore, the patient simulator provides a robust system which reactsupon user interaction with the lung model (for example, if the userchanges the inspired gas composition). Thus, when a user changes theinspired gas composition, this change causes changes to the physicallysimulated alveolar concentrations of the various gases. Thephysiological model will then determine the effects of these changes ingas concentrations in the lung and, in fact, upon the entirephysiological state of the integrated patient simulator. The lung modelphysically simulates these changes (for example, by decreasingspontaneous breathing). Furthermore, the lung model changes result in adifferent composition of gas being exhaled and thereby realisticallymeasured by the external monitoring instruments. Finally, the user mayreact to these changes by further changing the inspired gas composition,and thus initiating a cyclical repeat of the interactive steps describedabove.

Referring now to FIG. 1, it is helpful to gain a general understandingof the spatial orientation of the various subsystems of the preferredembodiment of the present patient simulator. The patient simulator 1consists of a manikin 4 placed atop a table 2. The table 2 itself is ofthe same physical dimensions as tables used in operating rooms andhospitals. Interposed in various positions below the table are thecontrol and implementation devices associated with several of thesubsystems of the integrated patient simulator.

Manikin 4 is constructed of plastic and has a means 54 for effecting athumb twitch as described in U.S. application Ser. No. 07/882,467. Inaddition, area 52 of this manikin indicates the general area forplacement of heart and lung sound devices subcutaneous to the manikin 4.A head 50 (Laerdal Medical Corp., Armonk, N.Y.) is provided attached tothe manikin 4. Head 50 contains the mechanism for simulation ofdifficult airway 700 (FIG. 8) and means for permitting cricothyrotomy(not shown). Attached to one arm of manikin 4 is a non-invasive bloodpressure monitor (NIBPM) 22. Signals from the NIBPM 22 are directed tocard 36 described infra.

Interposed beneath table 2 are various devices which will now bedescribed in more detail. Gas cylinders 6 are situated near the foot endof the manikin 4 in an array of gas cylinder holders 7. Attached to thegas cylinders 6 are regulators 8 for regulating the flow of gases.Cylinders 6 for O₂, CO₂, N₂ and N₂ O are provided. However, cylinders ofother gases may be added depending on need.

Just forward of the gas cylinders 6 are interposed various instruments10, 12 and 14. A pulse oximeter stimulator 10 is provided to stimulatethe pulse oximeter. Just below the oximeter stimulator 10 is placed anIV drug collection vessel with a digital scale 412 (Denver InstrumentCo., Arvada, Colo.) (See FIG. 5). Below the drug collection andquantification device, collectively labeled 12, is placed a NIBPMstimulator 14. The NEBPM stimulator 14 interfaces with NIBPM 22 andmodule 36 which in turn interfaces with the computer 16. Computer 16 issituated under the NIBPM stimulator 14 and next to a power supply 18capable of powering the complete patient simulator 1.

Situated behind instruments 10, 12 and 14 is a multiplexer 20responsible for the routing and handling of data signals for inputs andoutputs as utilized in the preferred star network configuration 501 (SeeFIG. 7). Adjacent to multiplexer 20 and power supply 18, is interposed arack 19 of plug in modules 28, 30, 32, 34, 36, 38, 40, 42 and 44. In thepreferred embodiment, module 28 is responsible for the generation ofheart sounds. Module 30 is responsible for the generation of the ECG.Module 32 is responsible for generating lung and breath sounds. Module34 is responsible for portions of the lung simulator the gas exchangeand mass flow controllers 122. Module 36 is responsible for the palpablepulses (not shown), NIBPM 22 and bronchial resistances (See FIG. 4).Module 38 is responsible for the drug identification and quantificationsubsystems. Module 40 is included for simulating machine and/orequipment failures of an anesthesia machine. Module 42 drives the thumbtwitch mechanism 54. Finally, module 44 drives other portions of thelung simulator: the lung mechanics 26 and the two EPRs 108 (See FIG. 2).Those skilled in the art would realize that other desirable modulescould be included in an expanded rack 19 end that the order of modulesis unimportant.

The lung assembly 26 (Michigan Instruments, Inc., Grand Rapids, Mich.,Dual-Adult Test Lung) is interposed below table 2 and manikin 4. Alsoshown is a pivot 24 point which is part of the bellows mechanism (SeeFIG. 2). Forward of the lung assembly is a gas analyzer 48 (HewlettPackard M1025A, Palo Alto, Calif.) into which is fed the gases from thebellows 100 of the lung 26. Opposite gas analyzer 48 is situated asyringe pump 58 and associated copper block mechanism 56 (See FIG. 3).

The various subsystems are connected as follows. Signals from computer16 are routed through multiplexer 20 and to the rack 19 of modules.Appropriate inputs are determined from sensors placed throughout themanikin 4, em., intravenous drug addition detection means. In addition,various outputs are routed rough the multiplexer 20 and via the modules28, 30, 32, 34, 36, 38, 40, 42 and 44 to appropriate output devices,including speakers for heart and lung sounds near 52, difficult airwaysimulation (See FIG. 8) 700 in the trachea area of head S0 (See FIG. 4),thumb twitch 54, movement of lung mechanism 26, etc.

By "physiological model," it is intended that the computer 16 mayregulate the behavior and interaction of the various subsystems so thatthey behave in a manner consistent with a human patient. Thus, dependingupon the parameters, e.g., sex, age, body mass cardiac output, shuntfraction, etc., the current invention allows the simulation of healthyand diseased (e.g., emphysema) patients of various ages and bothgenders. Other models may be rendered limited only by the scope ofmodeling desired. A particular desired physiological model could berendered by one skilled in the art with knowledge of the mathematicalbehavior of the systems to be simulated.

"By physiological state," it is meant the totality of all physicallyrelevant data, e.g., blood pressure, heart rate and cardiac outputs. Thephysiological state includes simulated temperature, gas content in thelungs, anesthetic drug involved including quantity and otherinformation. In addition, compliance of the lung, whether the patient isexhaling or inhaling, has a difficult airway or bronchial resistance areall factors which in their totality will dictate the physiological stateof the patient simulator 1. The list just described is expressly meantto be non-limiting, and the particular physiological information trackedwill depend upon the particular embodiment desired and the relevantphysiological model. The information about the physiological stateconstitutes the data used by computer 16 in implementing a particularphysiological model.

By "programmed computing means," it is meant the combination of thecomputer 16 which controls the single board computers, e.g., 508, whichmanage the various subsystems of the current patient simulator 1. Theprogrammed computing means thus exists atop a distributed processingnetwork 501 as described elsewhere herein and known to those skilled inthe art. The necessity to convert digital inputs and outputs to analoginputs and outputs is modeled as appropriate but such devices aregenerally not shown in the schematic figures. However, one skilled inthe art would readily be able to determine their necessity andimplementation, as well as the overall wiring scheme needed by examiningU.S. patent application Ser. No. 07/882,467 and the informationcontained herein.

Thus, time and event based scripts are run based on the computer 16intervention or instructor intervention with the system. The events maybe scripted or non-scripted as appropriate for the desired simulatedapplication. A combination of time- and event-based scripts is possiblewhere needed. For instance, an instructor may determine that a difficultairway situation should arise by using an event-based script. Inresponse, the physiological model is used to model the behavior of thesimulator in response to the scripted difficult airway event which isphysically created. The scripts readily interface with the physiologicalstate information as well as the physiological model.

The specific embodiments of the patient-simulator and methods of usingit are disclosed more fully in the following non-limiting examples ofthe best mode of carrying out the invention.

EXAMPLE I Self-regulating Mechanical Lung

During simulated spontaneous breathing, the breathing software modeldetermines a respiratory muscle activity based on arterial carbondioxide and oxygen partial pressures. This respiratory muscle activitydrives the mechanical lung model in the instant patient simulator bygenerating breaths of variable amplitude and frequency. The partialpressures of the gases inside the mechanical lung model (i.e.,"alveolar" partial pressures) depend on this breathing pattern, on thecomposition of the inspired gas and on the uptake or delivery of thegases to the alveolar space. The uptake or delivery is computed by asoftware physiological model and physically generated by a gassubstitution technique. The alveolar partial pressures (part of thephysiological state) are inputs to an uptake and distribution softwaremodel portion of the physiological model that computes the arterialcarbon dioxide and oxygen partial pressures.

During the simulation of normal conditions, the resulting alveolarventilation is sufficient to eliminate the carbon dioxide produced andto supply oxygen for consumption. Thus, in normal conditions,physiologically correct carbon dioxide and oxygen partial pressuresresult and the alveolar partial pressure can be approximated at the endof expiration by unaltered airway gas analyzers or monitors. Thearterial partial pressures are visualized on a modified continuous bloodgas analyzer (Puritan Bennett PB 3300, Lenexa, Kans.) (i.e, supplyingthe correct pressure, concentration, voltage, current, etc. signals) itthrough serial RS-232 links.

Under abnormal conditions, the self-regulating mechanical lung reacts ina realistic way to simulated conditions. Some conditions which may thusbe simulated include the administration of inspiratory gas containingtoo little oxygen or too much carbon dioxide, assisted ventilationcausing hyperventilation, (partial or complete) airway occlusion andinstructor controlled, simulation generated, or physiological modeldictated modification of programmable lung and thorax compliances. Inaddition, depression of simulated circulation in the cardiovascularsoftware model and simulation of drug treatment affecting spontaneousbreathing and/or circulation may also be accomplished by the currentpatient simulator.

A. Implementation of the lung mechanics

Referring to FIG. 2, the lung volumes are realized by mechanical bellows100. The volume of the bellows is derived from an-excursion sensor 118.The excursion sensor 118 consist of a rack 116 and pinion (not shown)arrangement. One end of the rack 116 is attached to the top plate 120 ofthe bellows 100. The other end of the rack 116 is free. The pinion isengaged into the rack 116 and has a shaft encoder (not shown)mechanically coupled to it. As the lung bellows 100 volume changes, therack 116 moves with the top plate 100 and rotates the pinion and thusthe shaft encoder. Thus, after initialization, the volume of each lungbellows 100 is known at all times. Note that there is one excursionsensor 118 for each of the two bellows 100 allowing independent volumemeasurement for simulated left and right lungs. The piston rod (a shaftattached to a pinion) 114 of the double acting piston 112 is attached tothe bottom of plate 120. As the lung bellows 100 volume changes, e.g.,as the plate 120 moves from its rest position to position 120', the rack116 moves with the top plate 120 and thus the pinion turn the shaftencoder 115. Thus, after initialization, the volume of each lung bellows100 is known at all times. There is a separate excursion sensor 118 foreach of the two bellows 100 used in the preferred embodiment.

The software on the personal computer 16 that drives the lung 26 uses ananalog respiratory muscle pressure signal generated by the softwarecontrol model of spontaneous breathing. In addition, the software modeluses the left and right lung excursions 118 as inputs. Based on theseinputs, the model computes the pressures exerted by programmednon-linear lung and thorax compliances. Left and right intrapleuralpressures follow from these computations. Computer-controlled electronicpressure regulators (EPRS) (Proportion-Air, McCordsville, Ind., model#QBITFEE050) 108 are fed with an inspiratory pressure signal (wherefrequency of the signal is the breathing frequency and magnitude is thetidal volume) causing them to then drive a double acting pneumaticpiston 112 (Clippard, Cincinnati, Ohio) (one for each lung). In additionto the EPR 108, there is a manual pressure regulator (MPR) 110responsible for imparting a constant (i.e., a bias or reference)pressure on the double acting piston 112. The MPR 110 of the presentinvention produces about 25 psig of constant bias pressure. However,those skilled in the art would appreciate that other, mechanicallyfeasible bias pressures are contemplated.

The force created by the piston 112 is equivalent to the force resultingfrom the intrapleural pressure, and the lung compliance on the naturallung. Based upon the above interactions, the bellows 100 realisticallysimulates tie pressure-volume (and thereby the pressure-flow)characteristics of the natural lung.

Various physiologic parameters under computer 16 control may be set andmodified in educational scenarios, include bronchial resistances 124,lung and thorax compliances, and intrapleural volume allowing for thesimulation of respiratory complications such as endobronchialintubation, bronchospasm, pneumothorax, and emphysema according to anappropriate physiological model.

B. Implementation of the gas exchange

Uptake and delivery of the alveolar gases inside the bellows 100 arephysically created by gas substitution. The gases presently contemplatedare O₂, CO₂, N₂, N₂ O, and one volatile anesthetic agent (i.e.,isoflurane, enflurane, or halothane) (M. L. Good, S. Lampotang, G.Ritchie, et al: Hybrid lung model for use in anesthesia research andeducation, Anesthesiology 71, p. 982, 1989). In gas substitution, aconstant gas flow rate with a variable composition, thereby constantlyflushing the bellows 100, simulates the pulmonary blood flow, carryinggases to and from the lungs. The vane pump 106 (GASI 0532, BentonHarbor, Mich.) of FIG. 2 realizes the constant, volumetric flow rate(and, because it is a rotational device, eliminates the vibrationassociated with a reciprocating device), and the computer 16 driven massflow controllers 122 (Omega Engineering, Stamford, Conn.) allow foradjustment of the inflow composition. Uptake and delivery are computedbased on the measured alveolar partial pressures (from the gas analyzer48) and venous partial pressures from the uptake and distributionsoftware model, taking into account perfusion and solubility.

Thus, gas is fed to the mass flow controllers 122 through feed lines 123originating in gas cylinders 6 and regulators 8. In addition, computer16 signals the MFCs 122 to provide a set flow rate of the appropriategas into tubing or conduit 102 which is resistant to volatileanesthetics. In the preferred embodiment, silicon tubing with a 1/8"diameter is used for conduit 102. The gas contained in the conduit 102is passed through a copper block 56 as described in FIG. 3. Input of anyliquid anesthetic occurs in the syringe pump assembly 58 (HarvardApparatus, Inc., Pump 22, South Natick, Mass.) and the volatilized gasis moved toward bellows 100 due to the flow of gases present in theconduit 102. In this way, gases are introduced via the conduit 102 Intothe bellows 100. Once in the bellows 100, gas pressure may be constantlyassayed using pressure sensors 101. In addition, down force of thebellows by movement of plate 120 on pivot 24 results in expulsion of gasfrom the bellows 100 through conduit 105. Conduit 104 leads to a gasanalyzer 48 where the gas continuously flowing from the bellows can beassayed for its constituents and their concentrations. In addition,conduit 104 leads to vane pump 106 which rotatably allows a constantflow rate of gas to escape to a scavenging area (not shown).

In addition, bellows 100 contains an aperture 103 leading to anadditional conduit 105. Conduit 105 is used by the simulated lung 26 toallow air to flow from the manikin 4 head to the lung 26. Along conduit105 there is a controllable bronchial resistance means 124 as describedherein with reference to FIG. 4. Conduit 105 continues on to the trachea(including difficult airway apparatus 700, shown in FIG. 8) and mouth ofthe manikin 4.

It should be noted that in the present embodiment, there are actuallytwo sets of bellows 100 and thus two double acting piston mechanisms112, one attached to each bellows 100 (although only one of each elementis depicted in FIG. 2). Thus, there are also two sets of MPR 110 and EPR108 included. In addition, each bellows 100 contains its own pressuresensor 101. However, most of the conduits 104 and 102 as well as thesyringe pump 58, vane pump 106, gas analyzer 48 and MFCs 122 are sharedbetween the simulated "right" and "left" lungs.

Thus, the present invention contemplates a method of simulating aselfregulated lung 26 in real time. The method includes step ofexpanding in volume at least one bellows 100 by a bellows actuatingmeans, e.g., a double acting piston 112, during an inspiratory phase. Agas flow from at least one mass flow controller 122 is allowed to flowthrough a conduit 102 to the bellows 100. The pressure inside thebellows 100 is under continuous monitoring based on the output from apressure sensor 101. This pressure output is used as one of the inputsto the physiological model coordinated by the computer 16. After theinspiratory phase is completed, an expiratory phase is created bycontracting in volume the bellows 100 by the piston 112 acting on plate120 as previously described. Before expulsion through the vane pump 106,gases transferred to the conduit 104 are analyzed in a gas analyzer 48which is situated intermediate the vane pump and the bellows in apreferred embodiment.

Furthermore, in a more preferable embodiment, a syringe pump 58 may besituated intermediate the mass flow controllers 122 and the bellows 100.The syringe pump S8 is responsible for continuously (as dictated by thecomputer 16) injecting a preselected flow rate of a volatile drug intothe gas flowing through conduit 102. The actual delivery of the liquiddrug to the gas flow is accomplished via the apparatus for receiving avolatile drug 56 described more fully below.

Furthermore, in a preferred embodiment, the bellows actuating meanscomprises a first constant pressure from an MPR 110 and a secondvariable pressure from an EPR 108 acting on respective sides of a doubleacting piston 112 whereby varying the second variable pressure causesthe bellows 100 to simulate an expiratory or inspiratory phase dependingupon a time- and event-based script, a computer model or a combinationof a time- and event-based script and a computer model based on thephysiological state of the patient simulator. For instance, thephysiological state may indicate that a cough is appropriate. If so, asignal is directed to the EPR 108 by the computer 16 indicating that arapid decrease in pressure is needed to simulate a cough. Thus, the EPR108 in responding to the signal will lower or raise the pressure againstone side of the double acting piston 112. This will create a pressureimbalance, the degree of which will determine the force and rapidity ofmovement of the piston 112. The double acting piston 112 by way of itslinkage through piston rod 114 and plate 120 will thus forcibly move thetop plate 120 of the bellows 100. Movement of the top plate 120 in anupward direction increases the volume of the bellows 100. This increasedvolume creates a slight subambient pressure in the bellows 100, therebymimicking inhalation or inspiration. Note that the opposite motion ofthe piston 112 via piston rod 114 would cause a concomitant expirationor exhalation thereby expelling any gases in the-bellows 100 due to thecreation of a slight positive pressure.

Thus, in a preferable embodiment, there is provided a self-regulatedlung in a manikin 4 for use in real time in an integrated patientsimulator during simulated medical procedures, comprising severalcomponents. The lung 26 uses at least one bellows 100 capable ofreceiving and expelling a gas. Furthermore, there is a means foractuating the bellows between an expanded and a contracted statedepending upon a time- and event-based script, a computer model or acombination of a time- and event-based script and a computer model basedon the physiological state of the patient simulator. Also present is atleast one mass flow controller 122 capable of directing the gas in tothe bellows 100. To transmit the gas flow there is a first conduit 102interconnecting the mass flow controller 122 and the bellows 100. Inaddition, a vane pump 106 capable of expelling the gas from the bellows100 is provided along a second conduit 104 interconnecting the bellows100 and the vane pump 106.

In a preferred embodiment, the means for a ting the bellows 100 betweenan expanded and a contracted state comprises a double acting piston 112attached to the bellows 100 at its top plate 120 via a rack 116 andpiston rod 114 is provided. A first constant pressure from an MPR 110and a second variable pressure from an EPR 108 act on respective sidesof the double acting piston 112 such that varying the second variablepressure causes the bellows 100 to simulate or undergo an expiratory orinspiratory phase. Furthermore, the pinion has a shaft encoder 115affixed thereto. This encoder 115 is a portion of the excursion sensor118, which is responsible for reading either the right or the left lungvolume of the bellows 100. This value is then used by the computer 16 tosimulate a response based upon the excursion value and other datacorresponding to the physiological state of the patient simulator 1.

An other preferred embodiment comprises the use of intrapleural pressuresensors 101 situated inside the bellows 100. These devices determine thepressure of the bellows which data form a part of the physiologicalstate of the patient simulator 1. Thus, the computer 16 may take intoaccount the intrapleural pressure so communicated in computing asimulated response of the system, e.g., determining compliance behaviorfor a particular physiological model based upon the instantaneous lungvolume reading.

Another embodiment of the lung 26 allows for placement of a commerciallyavailable syringe pump 58 disposed along the fist conduit 102intermediate the bellows 100 and the mass flow controller(s) 122,wherein the syringe pump 58 is capable of injecting a volatile drug intothe bellows 100. It should be noted that the conduits 102, 104, and 105used herein, as well as the other materials in contact with the gasflow, must be resistant to breakdown upon exposure to the volatile drugsused by clinicians. For this reason, silicon tubing is used for theconduits 102, 104, and 105 in the instant embodiment. However, othersuitable materials exist and would be known to one skilled in the art.

Finally, a gas analyzer 48 may be disposed along the second conduit 104intermediate the bellows 100 and the vane pump 106, wherein the gasanalyzer 48 is capable of assaying the expelled gases. The informationon expelled gases is then transmitted via an electric signal (not shown)to the computer 16. In the computer, based upon the currentphysiological model and physiological state, a simulated response to thegas analysis is computed. For instance, if no carbon dioxide is beingexpelled by the modeled lung 26, then an abnormal condition may bededuced in the physiological state.

EXAMPLE II Injection of Liquid Anesthetic Under Computer Control

Referring now to FIG. 3, the means for accepting the drug 56 comprises acylindrical copper block 202 with a hypodermic needle having a verysmall internal diameter (less than 0.01") accepting orifice 210 and asyringe pump S8 (not shown) for injection of liquid anesthetic. Thus, asintered brass (or other metal) insert 200 is placed in intimate thermalcontact within the solid copper cylinder 202 (6" long×2.5" diameter).The tip 214 of a hypodermic needle 208 is passed through a hole 210 (ofsufficient diameter to accept a commonly available syringe needle)drilled in the sintered metal insert 200 and secured via a manual pushfit. The other end of the hypodermic needle 208 is attached to the tipof a syringe (not shown) loaded with liquid anesthetic and mounted on acomputer-controlled syringe pump 58. The syringe is always placed at alower elevation than the point of injection so that the liquidanesthetic cannot unintentionally flow by gravity into the breathingcircuit.

In this configuration, the copper block 202 provides the thermal inertiaor heat capacity to prevent freezing at the point of anestheticinjection 214. The sintered insert 200 provides low flow resistance tothe passage of gas through the copper block 202, while allowing theliquid anesthetic to wick through it and thus be completely vaporized.The metallic nature of the sintered metal insert 200 provides intimatethermal contact and conduction as compared to, for example, a cotton wadas the injection point. (Ross, J. A. S., Wloch R. T., White D. C. &Hawes D. W.: Servocontrolled closed circuit anaesthesia: A method forthe automatic control of anaesthesia produced by a volatile agent inoxygen, British Journal of Anesthesia, 55:1053, 1983.) The flowresistance of the very small bore hypodermic needle 208 creates a backpressure of up to 15 psig at the syringe preventing the liquidanesthetic from spontaneously vaporizing at room temperature. Also, therate of injection of the liquid anesthetic and, therefore, the rate ofintroduction of inhalational anesthetic into the it is independent ofthe gas flow. The syringe pump 58 is controlled by computer 16 allowingfor ease of interfacing.

Thus, the instant invention contemplates a method of simulating aphysiological response to a drug in real time in an integrated patientsimulator during simulated medical procedures using a manikin. The stepsof this method include directing a volatile drug to a manikin 4 whichhas a drug receiving or volatilizing means 56 comprised of a thermalconductor 202 defining a gas propagating cavity 216 disposedtherethrough and a sintered insert 200 disposed within the gaspropagating cavity 216, the thermal conductor 200 future defining aneedle accepting cavity 210 which communicates the exterior of thethermal conductor 202 with the interior of the insert 200, wherein theneedle accepting cavity 210 is capable of accepting a hypodermic needle208 such that the tip 214 of the hypodermic needle 208 is in contactwith the sintered insert 200 when the needle 208 is fully inserted intothe receiving means 56, and wherein the gas propagating cavity 216 iscapable of permitting the flow of the gas 204 therethrough such that thedrug upon evaporation or volatilization in the sintered insert 200 iscarried through the gas propagating cavity 216 by the supply of gasflowing continuously therethrough and exiting opposite at 206.

Thus, a preferable embodiment comprises an apparatus for injecting andvaporizing a volatile drug in real time in a lung simulator duringsimulated medical procedures, comprising a manikin 4 and the systemdescribed supra. However, there is also a conduit (not designated) forinterconnecting the supply of gas 204 with the gas propagating cavity216.

In a preferred embodiment, the sintered insert 200 is comprised ofsintered brass and the thermal conductor 202 is made from a cylindricalpiece of copper with the gas propagating cavity 216 bored therethrough.

Thus, the design of this example has application beyond the instantpatient simulator. Practicing physicians, nurses and anesthesiologistswould benefit from the disclosed apparatus with only minor variations tothe concepts disclosed above. The combination of a syringe pumpinjecting liquid anesthetic through a very high flow resistancehypodermic needle into a sintered metal insert in a cylinder having highthermal capacity can be used as a computer controlled vaporizer in ananesthesia machine or anesthesia delivery system.

EXAMPLE III Simulation of Bronchial Resistances

Referring now to FIG. 4, a variable orifice device 124 disclosed hereinconsists of a nautilus shaped cam 304 which is able to progressivelyblock a lumen or conduit 300 or other delivery tube or pipe uponrotation of the cam 304 by a stepper motor 306. Motor control isaccomplished via module 36 sending a signal to the stepper motor 306. Ina preferred embodiment, the cam 304 is within housing 302 and isconstructed of thin flexible material (e.g., transparency film) used tovary the flow area through an off-enter flow passage 301. The patientsimulator 1 may have multiple bronchial resistance devices 124.

Gas 308 flows into the conduit 300 via the conduit's inner passage 301.Depending on the rotational position of the cam 304, the cam 304presents a selected surface within the passage 301 through an opening inthe conduit 300 so as to partially or totally restrict gas flowingtherethrough a long the direction 308 and out 310.

Specifically, the present invention discloses a method of simulatingbronchial resistance or dilation in real time in an integrated patientsimulator during simulated medical procedures using a manikin,comprising the step of actuating a means 124 associated with the manikin4 for restricting a simulated bronchial opening (as embodied by theinner passage 301 of a conduit 300, by rotatably (via a stepper motor306) engaging a nautilus shaped cam 304 which, upon rotation,continuously varies the size of the aperture of the simulated bronchialopening.

To accomplish this task, an apparatus (a variable orifice 124) forsimulating bronchial resistance or dilation in real time in anintegrated patient simulator during simulated medical procedures isdisclosed. In addition to the manikin 4 having a simulated trachea (notshown) and a simulated lung 26, the apparatus uses a volume of gas inthe direction 308 which enters a conduit 300 for propagating the gas.The gas 308 is used to simulate the flow of gases coming from thetrachea during inhalation. In addition, the bronchial resistance meansallows for the gas to travel in the opposite direction, from the lung 26to the trachea as in expiration. The conduit 300 interconnects thesimulated trachea and the simulated lung 26 and is interrupted by ameans 304 in the conduit 300 for restricting the flow of gas (in eitherdirection) therethrough whereby a bronchial opening is simulated andresulting in a restriction on the gas 308 flowing through the conduit300. In addition, any catheter or other device inserted into thesimulated bronchial opening will be impeded by the presence of abronchial resistance 124 means.

Such a device 124 provides the following advantages. First, changes inflow resistance can be physically realized in real time. Both the steadystate changes and the cyclical changes in airway resistance (variationbetween inspiratory and expiratory airway resistances during a breath)can be simulated. Each variable orifice 124 in each bronchus can beindependently controlled allowing the simulation of lungs with regionaldifferences in time constants. Because the flow of the gases to and fromthe lung will be physically impeded, the symptoms associated withincreased airway resistance will be automatically created. For example,the capnogram will be appropriately distorted (sloping, instead of flat,plateau) and the dynamic compliance will decrease with increased airwayresistance.

The pharmacologic effects of drugs like bronchodilators can be simulatedwith the variable orifice resistances 124, under control from apharmacologic model running on the control computer. Furthermore, asuction catheter or other probe can be passed down the bronchus when theflow orifice 124 is not closed. The instant device is capable ofproducing a multitude of flow-resistance curves. At least 10 differentflow resistance curves have been obtained.

EXAMPLE IV Detection and Identification of Intravenous Drug and FluidAdministration

Referring now to FIG. 5, an apparatus and associated system 12 isprovided wherein each syringe 400 and each IV bag 416 has a unique barcode label (402 and 418, respectively) that identifies the drug or IVfluid (including whole blood) as well as the concentration containedtherein. Furthermore, there is conveniently mounted a bar code scanner420 on an IV pole 422 (or some other convenient, fairly proximal item)next to the head 50 of the manikin 4. The trainee is instructed to scaneither the syringe 400 or the IV bag 416 by the bar code scanner 420(Metrologic MS941) mounted on the IV pole 422 before adminstering thedrug (which could be an intravenous anesthetic) or IV fluid. If thetrainee should turn on the IV manifold switch 406 (Baxter. Chicago,Ill.) prior to the scanning in of a drug identity, then a small warningbeep is emitted (not shown) to remind the trainee to use the bar codescanner 420.

An optical emitter/detector pair (the optical switch) 404 (Motorola.Inc.) is situated so as to transmit to the computer 16 an input/outputsignal indicating the physical status of the IV manifold switch 406,i.e, on or off. Thus, the system is able to determine whether the inputof medicament or fluid is being routed from the syringe 400 or the IVdrip bag 416.

The present invention discloses a method of detecting and identifying adrug administered in real time in an integrated patient simulator duringsimulated medical surgery using a manikin. The method requires thetrainee to scan a bar code 402 or 418 affixed to an implement which maybe either an intravenous drip bag 416 or a syringe 400, wherein therespective bar code indicates the type and concentration of drugcontained within the implement. It should be noted that any means ofcontaining a drug and delivering it to the patient simulator 1 could beused with the bar code system described herein. Next, a bar code scanner420 is used to scan the bar code. The scanner 420 is connected to thecomputer 16 such that the bar code which was scanned can be translatedinto computer usable information about the drug so detected andidentified.

Thus, the detection and identification of drug and IV fluidadministration is automatically performed, enhancing the realism of thesimulation. The system is also made more robust because an instructorwho may be distracted is no longer required for the drug identification.

EXAMPLE V Drug and IV Fluid Quantification

FIG. 5 also shows a means for drug and IV fluid quantification. In apreferred embodiment, it is desirable to achieve a measurement accuracyof ±0.25 ml for drugs injected via a syringe 400. An IV manifold 407 isprovided so that fluid can flow either from an IV bag 416 or from asyringe 400. A switch 406 must be manually turned on to select a fluidinlet to be connected to the intravenous needle (not shown) in themanikin 4. The switch 406 was equipped with an optical emitter-detectorpair 404 mounted on its underside (out of view of the user) whichtransmits a signal to the module 38 detailing the position of the IVmanifold switch 406 at all times. The light path between the emitterdetector pair 404 is interrupted when the switch is turned to injectdrug via the syringe 400. An interruption of the light beam causes aninput/output (10) bit to change state on the microcontroller board (oneof the single-board computers on the star-network 501).

As it is administered by the trainee, the IV fluid or drug 410 isemptied into a bucket 408 placed on a digital scale 412 (DenverInstruments, D1-5K, Arvada, Colo.). The digital scale 412 used hereincontains a serial port (not shown) for outputting information alongcable 413 to module 38 (not shown) to a computer 16 or other electronicdevice. The weight on the digital scale at the moment switch 406 isturned on is recorded by a computer in module 38 polling the serial porton the scale 412. When the switch 406 is turned back to its originalposition after the drug in the syringe 400 has been injected, the bitconnected to the emitter-detector pair 404 again changes state. Theinitial weight read by the scale when the IV manifold switch 406 isturned on is subtracted from the new weight on the scale 412. The weightdifference can be used to determine the volume and thus the amount ofdrug injected from the syringe 400 because the concentration is knownfrom the bar code 402 or 418 label on the syringe 400 or IV bag 416.

Furthermore, by polling the digital scale 412 at known time intervalswhen the IV manifold switch 406 is in the IV drip position, the rate ofIV fluid administration can be calculated by dividing the change inweight over a given time interval by the time interval. The type of IVfluid administered (Ringer's lactate, saline, etc.) will already havebeen identified by the bar code scanner 420 as described in Example IV.

Thus, them Is disclosed a method of quantifying the amount of a drug orIV fluid administer i real time in an integrated patient simulatorduring simulated medical surgery using a manikin 4. This method requiresthat the initial weight of a reservoir 408 first be determined. Thereservoir 408 should be capable of containing a suitable volume of drugadministered. In addition, the reservoir 408 need not be emptied aftereach application of a drug, but instead, the weight of the fluid In thereservoir may be used to determine when the reservoir 408 i almost full.Thus, the initial weight of the reservoir 408 may include an amount ofdrug 410 already contained therein. This is obviated by the use of adrip bag 416, where, over time, the reservoir 408 will fill and thus theinitial weight for determining the amount administered during therelevant time period will be ever increasing.

An initial weight is determined from the digital scale 412. Next, a drugis delivered to the reservoir 408. In the present embodiment, thedelivery is accomplished by diverting drug flow from the implementchosen, e.g., the syringe 400 via the manifold 407 to the reservoir viaa conduit (not shown) or some other means. After the occurrence of apreselected event, a second weight is determined by polling the digitalscale 412. This polling may be initiated by the computer in module 38which is connected via a serial link to the scale 412 so that thereading may be transmitted to the computer 16 for processing. Thepreselected event may be that a certain amount of time has passed, orthat the trainee has finished administering an injection. To determinethe actual weight of drug administered, it is simply necessary for thecomputer 16 to subtract the initial weight from the second weight. Basedon the difference value so computed, the patient simulator 1 thendetermines via the computer 16 a simulated response according to a time-and event-based script, a computer model or a combination of a time- andevent-based script and a computer model based on the physiological stateof the patient simulator 1. A skilled artisan would appreciate that asyringe and an IV drip bag am not the exclusive implements useful forpracticing the invention.

Also disclosed in conjunction with this method is an apparatus forquantifying the amount of a drug administered In real time in anintegrated patient simulator during simulated medical surgery.

EXAMPLE VI Star Network for Distributed Prosing

Referring to FIGS. 6 and 7, a star network is used as the distributedprocessing network of the instant invention. The star network 501 ofsingle board computers is implemented via a computer 16 and amultiplexer 20, using an RS-232 serial interface protocol. Distributedprocessing allows the parallel processing of different tasks. Theinherent robustness of the star network makes the simulation lessvulnerable to failure of any of the single-board computers 506, 514, . .. on the network (unlike in a ring configuration as depicted in FIG. 6).

It is instructive to first examine a ring network 600 as shown in FIG.6. In FIG. 6, a computer 16 is used to drive a master microcontrollerboard 606. A signal is firs sent out via line 608 to a first singleboard computer 602. That computer 602 determines whether it needs tohandle the signal or not. In addition, the signal is allowed to passalong path 608 to the next computer 604. In this manner, a serialcircuit is traversed by the signal using pathways 608. If any one of thecomputers, e.g. 602 or 604 fails, then the entire network 600 will fail.

The use of a star network 501 as depicted in FIG. 7 overcomes thissignificant problem. It is instructive to examine the flow of theelectric cardiac synchronization pulse 500 along the star network 501.First, the computer 16 generates the pulse 500. The pulse is convertedvia a digital to analog converter card 502 into an analog signal 504.This signal is transmitted along a cable to the backplane 516 of thestar network 501. There, the signal is in effect transmitted to eachsingle board computer, e.g. 508, in parallel via junctures 506, 514, . .. synchronizing all cardiac related events.

The single board computer, e.g, 508, has two-way communications via line510. Finally, the multiplexer 20 has two-way communication also with thecomputer 16 via line 512. In sharp contrast, however, to the ringnetwork 600 of FIG. 6, if one of the single board computers, e.g, 508,happens to fail, a signal such as a cardiac pulse signal 500 will not berendered undeliverable to the other single board computers due to anopen circuit such as in a serially configured ring network 600. instead,the malfunctioning unit will simply not contribute to the patientsimulator system 1.

EXAMPLE VII Triggering Scheme for Cardiac Rhythm Related Events

The current invention also provides a triggering scheme for cardiacrhythm related events. This scheme consists of a synchronization pulse500. See FIG. 7. Within the software physiological model 520 programmedinto the computer 16 (a first programmed computing means) that drivesthe patient simulator 1, there is an ECG waveform generator 518. The ECGwaveform generator 518 outputs the frequency and pattern of the ECG. TheECG waveform generator also outputs the synchronizing pulse 500 via aD/A converter 502 that gets delivered to all computers, eg 508 (a secondprogrammed computing means), on the star network 501 that require theelectric cardiac rhythm synchronizing pulse 500. Thus, both arrhythmiasand normal sinus rhythms are instantly simulated and displayed on theappropriate subsystems and monitors.

A time offset to allow for travel time or lag of the cardiac pulsethrough the body can be added at the local single board computer level,e.g. board 508. For example, in a real patient, the cardiac pulse willappear sooner at sites closer to the heart, e.g., the carotid pulse,compared to sites further from the heart, e.g., the radial pulse. Thus,although the carotid and radial pulse will be at the same frequenciesand exhibit the same arrhythnias, the simulated pulses can be madestaggered in time by adjusting a time delay at the local board level, SO508.

Thus, there is disclosed a method of synchronizing cardiac rhythmrelated events in real time in an integrated simulator during simulatedmedical procedures using a manikin. The method requires the transmittingthroughout a distributed processing network 501 or 600 associated withthe integrated patient simulator 1. As noted above, it is preferable ifthe distributed processing network is a star network 501.

Using this method, it is thus possible to actuate various subsystemdevices associated with the manikin 4 such as radial pulses. The radialpulse, because of its distance from the heart, can be delayed asdictated by the software model operating on the relevant single-boardcomputer, e.g., 508.

Also provided is an apparatus for synchronizing output devices relatedto a cardiac rhythm in real time in an integrated patient simulatorduring simulated medical surgery. This apparatus uses a manikin 4 withat least one output device. At least one electric cardiac rhythmsynchronizing pulse 500 is distributed over the distributed processingnetwork 501 as described supra. It is preferable that the distributedprocessing network is a star network 501.

EXAMPLE VIII Simulation of Lung and Heart Sounds

Similarly, the lung sounds associated with a certain lung field shouldbe at that specific lung field in area 52 of the manikin 4 and notanother location. Further, depending on the physiological condition ofthe patient being simulated, the sounds will be either normal orwheezing. Various other sounds, such as sounds indicating abnormalphysiologic states, may also be simulated.

To accomplish simulation of lung and heart sounds, it is advantageous tostore various different banks of sounds of breathing on analog memoryintegrated circuits. In the preferred embodiment, ISD 1016AP integratedcircuit chips (Information Storage Devices, Inc., San Jose, Calif.) areused to effect the simulation of various sounds. These chips possessDirect Analog Storage Capability (DASI), whereby the information from ananalog input source is stored directly into and read directly fromstandard electrically erasable programmable read only memory (EEPROM).DAST (capable of storing signals of up to 230 distinct voltage levels)allows storage of up to eight times the information per cell compared todigital solutions (allowing for only two voltage states, i.e, a bit iseither on or off). Since EEPROM is non-volatile, no battery back-up isrequired to preserve recorded information and overall power consumptionis significantly reduced. Thus, EEPROM are particularly suitable toremote or portable embodiments.

Within the ISD 1016AP integrated circuit, filters, preamplifiers,automatic gain control and speaker drivers have been included in asingle chip. Thus, the ISD 1016AP used in the instant patient simulatoris a complete single chip solution. Thus, only a microphone, speaker anda power supply am needed to create a complete record/playback system.

When the appropriate triggering signal is transmitted to the appropriatechip, the analog signal encoded therein is played to the appropriatespeaker located in the vicinity of area 52 of the manikin 4. Most soundsfor the present invention are cyclical (e.g., heart beat), or biphasic(e.g., inspiration and expiration sounds of breathing) in nature thuslending themselves to DAST chip suitability.

Referring now to FIG. 9, which encompasses area 52 of manikin 4, heartsound speakers are located at the right upper sternal border 800, leftupper sternal border 802, left lower sternal border 840 and the apex806. In addition, speakers for outputting lung sounds are located at theright apex 808, the left apex 810, the right lateral. 812 and leftlateral 814 positions. A subcutaneous simulated sternum 818 and nipples816 are indicated for reference.

In addition, the sounds heard over the lung fields 52 are differentaccording to respiratory phase i.e. inhalation or expiration. Thus,proper synchronization of lung sounds produced by the DAST chips isnecessary to avoid negative reinforcement due to the incorrect soundbeing omitted (e.g., expiratory sounds while inhaling).

The first derivative with respect to time of each lung volume obtainedby excursion sensor 118 is calculated to determine the phase of therespiratory cycle. The second derivative is used to detect thetransition from inspiration to expiration and vice versa, whichtransition occurs at a time when the second derivative of lung volumewith respect to time is zero. The ECG respiratory patter (generated inthe ECG signal generator 518) of the present patient simulator 1 isinfluenced by the respiratory pattern and phase and the physiologicalmodel 520. The actual movement of the bellows 100 triggers theproduction of appropriate lung sounds.

In order to simulate sounds (heart, lung, esophageal, bowel, etc.) inthe correct locations, an array of small speakers (not shown) isdistributed below the skin of the manikin 4 at the appropriate locations(near area 52). The appropriate sounds am supplied to appropriatelocations under the control of a triggering scheme dictated by thecontrol computer 16.

Furthermore, changes in sound are used to reflect abnormal physiologicalconditions. Auscultation has been traditionally used to diagnose thecondition of a patient and forms a significant portion of the trainingof medical students. Thus, septal and valvular defects in the heart maybe detected by lilting for certain sounds associated with theseconditions.

In the present patient simulator, sounds associated with abnormalphysiological conditions (e.g., heart valve defects) are stored and whenappropriately triggered are sent to the proper location (speaker) on themanikin 4.

Breathing sounds may also be simulated. Thus, the current inventioncontemplates a method of simulating sounds of breathing in real time inan integrated patient simulator 1 during simulated medical proceduresusing a manikin 4, comprising the steps of continuously determining thevolume (via an excursion sensor 118, for example) of at least onebellows 100 associated with the manikin 4. Using standard mathematicalprocedures based on the time and the volume determined, it is thennecessary to calculate a first derivative of the bellows volume overtime to determine the phase of the respiratory cycle. Furthermore, bycalculating a second derivative of the bellows volume over time, it ispossible to determine a transition in phase of the respiratory cycle(e.g. inhalation to exhalation or vice versa). Based upon the first andsecond derivatives of the bellows volume over time, a sound is output ordirect to and through a sound outputting means, such as a speakerlocated at an appropriate place, e.g., the mouth of the manikin 4. Thesound may be an audible sound of breathing corresponding to anappropriate physiological sound.

In addition, based upon the physiological state of the patient simulator1, it is possible to determine whether an abnormal condition exists. Ifso, then the patient simulator 1 will alter the audible sounds ofbreathing corresponding to the appropriate physiological sound basedupon the abnormal condition effecting the physiological state.

To accomplish these methods, a related apparatus for simulating ofbreathing in real time in an integrated patient simulator duringsimulated medical procedures is also disclosed. The relevantphysiological sounds are prerecorded onto the analog chips describedabove. The outputting means is similar to that detailed supra.

In addition to sounds of breathing, heart and lung (or lung field)sounds are also disclosed by the current invention. Thus, there isdisclosed a method of simulating heart sounds in real time in anintegrated patient simulator during simulated medical procedures using amanikin. At an appropriate time, duration and frequency, a soundoutputting means is activated which emits an audible heart sound or lungsound to the pertinent speaker corresponding to an appropriatephysiological sound output location (see FIG. 9). As in the simulationof sounds of breathing, the method also contemplates a step ofdetermining whether an abnormal condition is effecting th physiologicalstate and, if so, altering the audible heart or lung sound correspondingto the appropriate physiological sound based upon the abnormal conditioneffecting the physiological state. This alteration may occur through anyappropriate means including a programmed computing means such as acomputer 16. Breathing sounds may also be similarly altered.

To accomplish these tasks, the current invention includes an apparatusfor simulating heart and lung sounds in real time in an integratedpatient simulator during simulated medical procedures. The device hasbeen described more fully supra.

EXAMPLE IX Simulation of Continuous Blood Gases

Modern clinicians now have available a device which allows nearlycontinuous monitoring of blood gases (pO₂, pCO₂, pH, temperature)through an in-dwelling probe placed in the artery of a patient.

The instant patient simulator is capable of emulating the behavior ofthis new device. Using a physiological model of the cardiovascular andpulmonary systems, the appropriate readings can be artificiallygenerated depending on the state of the patient simulator system 1.These outputs are channeled through a serial port to the display panelof a mock-up of a continuous blood gas analysis device (not shown).Thus, a real-time continuous display of blood gases is available asanother realistic source of information for the trainee to react to. Thedevice thus allows the student to see the interaction between theinvasive blood gas analysis and other parameters obtainednon-invasively, e.g. pulse oximetry.

Thus, the present invention discloses a method of simulating themonitoring of continuous blood gases in real time in an integratedpatient simulator during simulated medical procedures using a manikin.The simulation requires the knowledge of the current arterial blood asvalues generated by the physiological model. The information about thestate will include such items as simulated blood pH, temperature, andarterial O₂ and arterial CO₂ partial pressures. Based upon thephysiological state being simulated, the physiological model willdetermine the above appropriate blood gas information. With thisinformation, the computer 16 will actuate a mock continuous blood gasmachine (not shown) according to the appropriate blood gas information.

To accomplish this simulation, the current invention discloses anapparatus for simulating the determination of continuous blood gases inreal time in an integrated patient simulator during simulated medicalprocedures. The apparatus comprises a manikin 4 interconnected with amock continuous blood gas machine (not shown). The mock blood gasmachine is actuated via electronic signals from the computer 16depending upon the physiological state and model. Thus the mock bloodgas machine has a means for simulating an output. Thus, the displaypanel is under the control of the computer 16 of the patientsimulator 1. There is also a means, preferably a cable, for delivering asignal to the mock blood gas machine in order to create a simulatedoutput in real time.

EXAMPLE X PA Catheter Inflation Detection

The pulmonary arteries (PA) catheter is used to measure these patientparameters related to cardial performance, pulmonary artery pressure(systolic, diastolic, and mean), pulmonary artery occlusion ("wedge")pressure (left ventricular end diastolic pressure LVEDP, an indicator ofleft ventricular filing) and cardiac output.

The PA catheter is introduced via the jugular vein (near the neck) orthe subclavian vein into the superior vena cava, through the rightatrium, right ventricle and into the pulmonary artery. When the PAcatheter balloon is not inflated, the PA catheter measures systolic anddiastolic PA pressure. When the balloon is inflated, the drag on theballoon from the blood "floats" the balloon downstream into thepulmonary capillary bed where it gets "wedged" as the PA diameternarrows down. The pressure measured after the balloon is inflated iscalled the wedge pressure which very closely approximates the LVEDP Inmost patients. Therefore, after the student on the simulator inflatesthe PA catheter balloon, a change in the PA pressure trace is expectedwithin 1 to 10 seconds.

The present invention provides an apparatus 900 for determining theinflation of a pulmonary artery catheter balloon 914 in real time in anintegrated patient simulator during simulated medical procedures. Theapparatus has a housing 910 defining a catheter receiving cavitytherein. A lever 916 is pivotally mounted on a pivot 902 on the housing910. The lever has a first end 917 and a second end 904 where the firstend 917 is movable in response to the inflation of the balloon 914. Alsoincluded is a means 906 for detecting the position of the second end 904whereby when the balloon 914 is inflated a signal 908 is generated bythe detecting means 906 to indicate the inflation.

This signal 908 is used by the programmed computing means in calculatingthe appropriate physiological response to whether the PA catheter tip912 and the balloon 914 attached thereto has been inflated.

EXAMPLE XI Difficult Airway

Referring now to FIG. 8, there is shown a means for simulating adifficult airway 700 on the patient simulator 1. The means forsimulating a difficult airway 700 provides a method of demonstrating theeffects of certain kinds of reactions, such as allergic, wherein thetrachea (a flexible airway) constricts. If an ETT tube cannot beinserted into the trachea before complete constriction, the patient isnot able to breath, obviously resulting in a serious condition. Theclinical solution is to perform an emergency cricothyrotomy whichentails puncturing a hole in the front of the trachea so that air mayflow below the point of constriction and into the lungs.

The means for simulating the difficult airway 700 of the instantinvention entails modifications to the head 50 of the manikin 4. Themodified head 50 uses an approximately 1" diameter hose or conduit 712attached to the neck portion. The shape of this conduit 712 is "D"shaped with the flat portion of the "D" 722 aligned with what would bethe back of the neck. A horseshoe shaped holding clamp 710 is fittedover the exterior surface of the semicircular wall of the "D" 726. Uponthe proper actuation of a pneumatic actuator line 702, a pneumaticcylinder 706 forces a plunger 708 into contact with the linear portionof the "D" 722. Enough force is transmitted to completely occlude theairway 711 thus resulting in a difficult airway. Upon removal of theactuation signal, the pneumatic cylinder 706 discontinues forcing theplunger 708 forward and the spring return 704 retracts the plunger 708.

The trainee faced with a difficult airway situation must perform acricothyrotomy. To do so, the trainee uses a traecheastomy kit 714 topuncture a hole into the trachea at an appropriate location. On theinstant patient simulator 1, the puncture is made in a replaceablemembrane 716 (NAFCO, location Tex.).

More specifically, the difficult airway system 700 is an apparatus whichsits in the neck of the head 50 of the manikin 4. Thus, if theinstructor chooses to simulate a difficult airway, then a means forconstricting, crushing or sealing a flexible airway 711 in the neck ofthe manikin 4 is actuated.

In the preferred embodiment, flexible airway 711 comprises a conduit 712having a flat back wall 722 having opposed, parallel sides therealongand an interior surface 720 and an opposed exterior surface 718. Theairway 711 also has a semicircular front wall 726 which has edgesconnected to respective sides of the flat back wall 722. Wall 726 alsohas an interior surface 724 and an exterior surface 728. In addition,there is a plunger 708 disposed adjacent to the exterior surface 718 ofthe flat back wall 722. To effect a difficult airway, there is also ameans for actuating the plunger 708 (for instance, the means could be apneumatic cylinder 706 activating the plunger 708 capable of forciblycrushing or sealing the flexible airway 711 with a spring return 704 forretracing the plunger), whereby the plunger 708 engages the exteriorsurface 718 of the flat back wall 722 so as to move the interior surface720 of the flat back wall 722 a selected distance toward the interiorsurface 724 of the semicircular front wall 726. This motion thus crushesor seats the flexible airway 711 upon sufficient movement of the plunger708. In a preferred embodiment, the plunger 708 is complimentarilyshaped to the interior surface 724 of the semicircular wall 726. Thus,the present invention discloses a method of simulating a difficultairway 700 in real time.

EXAMPLE XII Gas Exchange With Mass Flow Controller

Referring mainly to FIG. 2, it is desirable to create realisticsimulated uptake and delivery of respiratory gases such as oxygen,carbon dioxide, nitrous oxide and nitrogen along with the volatile andanesthetic gases in the mechanical lung 26. The present invention usesgas substitution to implement this function. With gas substitution, aconstant amount of gas is removed from the lung and its compositionanalyzed in real time by a gas analyzer 48. For each gas, uptake anddelivery is modeled by permitting an appropriate inflow of that gas(through conduit 102 and into the bellows 100).

Thus, for example with oxygen, the oxygen inflow rate may be calculatedas equal to the oxygen fraction times the outflow rate minus the desiredoxygen uptake measured in liters per minute. Thus, continuouslycontrollable mass flow controllers 122 were used to create the requiredinflow rates of nitrogen, oxygen, nitrous oxide and carbon dioxide.

The vane pump 106 of the pent invention creates an outflow rate whichdepends upon the bellows 100 pressure. The outflow rate for theparticular implementation described herein is:

outflow rate=3+0.032 times the bellows pressure.

This value is substituted in the oxygen inflow rate formula of thephysiological model to compensate for the increase in oxygen outflowrough the vane pump 106. The bellows pressure is measured by pressuresensors 101.

The continuous flow rates allowable by the MFC's 122 give rise to moreprecise, smoother adjustment of gas composition in the bellows 100,thereby reducing the pressure fluctuations associated with othertechniques. Pressure compensation avoids unrealistic readings as wouldresult with pulmonary pressures applied during routine ventilation inanesthesia.

EXAMPLE XIV Simulation of Non-linear Compliances

The ability to control lung compliance by computer without manualintervention is desirable because a real patient sometimes undergoeschanges in compliance during anesthesia, e.g., during thoracic surgerywhen the surgeon opens the chest cavity. The patient simulator of thepresent invention provides a means for simulating compliance curveswhich are non-linear, i.e, sigmoidal in nature and thus more realistic.

The purpose of the mechanical lung 26 aspect of the patient simulator isto reproduce the airway pressure-flow characteristics and gascomposition of the natural lung in normal and pathophysiologicconditions arising during anesthesia. One important aspect of thepressureflow characteristic is compliance. Static compliance is definedas the increase of lung volume divided by the increase in pressure usedto create that increased volume. Existing lung models implementcompliance with springs and/or compressible gas chambers. That type ofmodeling makes computer control over compliance cumbersome. In theinstant patient simulator, compliance is a variable in the controllingcomputer and can be rapidly changed via computer.

The lung volumes are realized by mechanical bellows 100. The volume ofthe bellows 100 is derived from the excursion sensor 118 attached toeach of the two belows 100 (although, as previously noted, only one isshown). Based on the excursions, respective lung volumes are computed.The double acting pneumatic piston 112 (one for each lung) then createsa volume dependent downward force on the bellows 100 due to adifferential in pressure from the EPR 108 versus the MPR 110 that isequivalent to the computer 16 force that would be opposing inflation dueto the lung compliance.

The means for accomplishing non-linear compliances is through the use ofthe double acting piston 112. One side of the piston is exposed to abias pressure from a manual pressure regulator (MPR) 110 while the otherside of the piston is exposed to a pressure from an electronic pressureregulator (EPR) 108. The EPR 108 is computer controlled via adigital-to-analog (D/A) line (not shown). The D/A line is supplied withthe muscle press signal described elsewhere herein. Thus, in addition tonormal lung activities and compliances, a cough may be simulated bysuddenly lowering the pressure of the EPR 108 below that of the biaspressure of the MPR 110.

Thus, the present invention discloses a method of simulating non-linearcompliances in real time in an integrated patient simulator 1 duringsimulated medical procedures using a manikin 4. The method includes thestep of fit computing the volume of at least one bellows 100. Volume ispreferably determined via the excursion sensor 118 output describedelsewhere herein. Based on the volume reading and optionally a readingfrom the pressure sensors 101 situated in the lung the compliances maybe modeled. The modeling itself is embodied in the use of a bellowsactuating means which has a first constant pressure from an MPR 110 anda second variable pressure from an EPR 108 acting on respective sides ofa double acting piston 112 capable of actuating the bellows 100 wherebyvarying the second variable pressure causes the bellows 100 to exhibitthe desired compliance force on the bellows 100 according a time- andevent-based script, a computer model or a combination of a time andevent-based script and a computer model based on the physiological stateof the patient simulator 1.

In generating a compliance, the volume measured by the excursion sensor118 is used as one input in a predetermined mathematical complianceformula dictated by the physiological model. The output of themathematical compliance formula is the desired or target lung pressure.

What is claimed is:
 1. An apparatus for simulating bronchial resistanceor dilation in real time in an integrated patient simulator duringsimulated medical procedures, comprising:a. a manikin with a simulatedtrachea and a simulated lung; b. a conduit interconnecting the simulatedtrachea and the simulated lung for propagating a flow of gas; and c.means for variably restricting the flow of gas through the conduitwhereby a bronchial opening is simulated.
 2. The apparatus of claim 1,wherein the conduit is interrupted by an opening and wherein therestricting means comprises:a. a nautilus shaped cam; and b. means forrotating said cam such that a selected surface of said cam is disposedwithin said opening so as to continuously vary the size of the opening.3. The apparatus of claim 2, wherein said means for rotating said camcomprises a stepper motor.
 4. A method of simulating bronchialresistance or dilation in real time in an integrated patient simulatorduring simulated medical procedures using a manikin, comprising the stepof actuating a means associated with the manikin for restricting asimulated bronchial opening by rotatably engaging a cam that presents aselected surface thereof within an opening in a conduit so as to varythe size of the opening.
 5. The method of claim 4, further comprisingpropagating a flow of gas in a first direction to simulate inhalationand in a second direction to simulate expiration.
 6. The method of claim4, further comprising the step of simulating the pharmacologic effectsof drugs on bronchial resistance or dilation.
 7. A method of simulatingbronchial resistance or dilation in real time in an integrated patientsimulator, comprising the step of variably restricting a simulatedbronchial opening associated with the integrated patient simulator. 8.The method of claim 7, wherein the step of variably restricting asimulated bronchial opening is carried out by rotatably engaging a camthat presents a selected surface thereof within an opening in a conduitso as to vary the size of the opening.
 9. The method of claim 7, furthercomprising propagating a flow of gas in a first direction to simulateinhalation and in a second direction to simulate expiration.
 10. Themethod of claim 7, further comprising the step of simulating thepharmacologic effects of drugs on bronchial resistance or dilation.